My present invention relates to a rerouting device for a safety belt and, in particular, for a seat belt of a vehicle and which is adapted to be mounted on a support element and the vehicle and to have a seat belt guided therethrough in changing directions between the belt buckle and hence the user, and the device from which the seat belt pulls out and which locks the seat belt in the case of an accident.
Such a rerouting device is commonly provided with an elongated eye through which the seat belt runs and which can have a riding surface against which the seat belt bears when the seat belt is tightened.
Rerouting devices of the aforementioned type are widely used in automobiles and the seat belt is usually threaded through the eye. The rerouting device in changing directions between the individual to be protected and the reserve from which the seat belt can be drawn and which may be provided with a locking unit adapted to grip the seat belt in the case of an accident.
Such a rerouting device can comprise a sheet steel body which can be stamped to form riding surfaces along which the seat belt is guided as it is pulled through the eye in one or the other direction.
The rerouting device is widely used for so-called three-point seat belts in automotive vehicles and can be mounted, for example, on the B-column of the vehicle and can then pivot to accommodate movement of the seat belt and the individual.
The rerouting device is usually subject to stress in the case of an accident and the substantial deceleration of the vehicle which results therefrom and must be capable of holding the seat belt against the mass of the person. The belt tension, tautness and belt-force limiting devices affect the load applied to the rerouting device. It has been proposed to provide a prefabric coating, for example a chromium coating, for belt riding surfaces of such devices to reduce the friction resistance of the sliding of the belt in the device. Such friction reduction permits the belt to slide more freely in the rerouting device and prevents overheating and hang-up of the belt in the device, even in a crash situation when relatively high relative speeds of the belt and the rerouting device can occur. Excessive heating not only creates a risk of damage to the seat belt by a melting thereof but also can result in injury of the belted individual. However, the rerouting device in that case has unsatisfactory values of the friction coefficient although it does have good wear resistance and a long useful life.
It is also known to provide rerouting elements with metal cores and a relatively thick plastic jacket. The plastic jacket forms the belt-riding surfaces. The friction coefficient of this plastic sheet or jacket is less than that of a chromium layer. Moreover, the plastics which have been used tend to have low temperature resistance and thus tend to wear readily and to be useless when heated to a significant extent as can happen in the case of a crash when the belt passes through the rerouting device at high speed. In these cases the plastic can soften and even melt locally. These effects are detrimental to the heating properties of the belt in the rerouting device and can represent drawbacks as well when the seat belt is to be effective in a crash. The plastic jacket tends to have small cracks which may be insignificant on fabrication but which, in the case of a crash, are subjected to a high degree of loading and deterioration or full breakaway. The resulting edges of the remaining plastic or metal edges which are liberated can contribute to the tearing of the belt and in extreme cases can result in separation of the belt.
DE 195 15 562 describes a rerouting device that utilizes a metal rerouting element to which a thick synthetic resin coating is applied and which has a throughgoing recess in the region of the outer edge of the metal part. This recess forms a weakened region whose rupture in the case of a crash does not affect the function of the plastic coating since the rupture does not occur in the region of belt travel. The rupture does not, however, solve the problem of cracks in the plastic part. Furthermore, when the plastic covering is relatively thick as described, thermal conduction of friction heat away from the coating is unsatisfactory in the case of a crash.
DE 299 15 058 describes a sheet steel rerouting element with a coating for reducing resistance. The coating materials here described include polytetrafluoroethylene. While this material has a high temperature resistance, its wear resistance leaves much to be desired and for long-term use, the material is scarcely suitable.
It is the principal object of the present invention to provide an improved rerouting device for seat belts and the like whereby the aforementioned disadvantages can be avoided.
More particularly, it is an object of the invention to provide a rerouting device which has a long useful life, low heating friction coefficients between the guide surfaces of the rerouting devices and the belt and which nevertheless has good resistance to high temperatures and an excellent ability to dissipate heat.
These objects are attained, in accordance with the invention, in a rerouting device for a seat belt for a motor vehicle, particularly a passenger vehicle, which comprises:
a sheet steel body formed with an elongated eye through which a seat belt can be passed, a belt riding section around which the seat belt can be bent and which is engaged by the seat belt as it passes through the eye, and a portion adapted to be fixed to a supporting portion of a vehicle body; and
a friction-reducing synthetic resin coating at least on seat belt-engaging surfaces of the belt riding section, the synthetic resin coating being composed of a fluoropolymer matrix containing reinforcing substances dispersed therein and having a thickness of less than 100 xcexcm. The fluoropolymer matrix consists preferably of polytetrafluorethylene. The reinforcing substances are particles of materials having a low friction coefficient. A possible reinforcing substance with a low friction coefficient is molybdenum disulfide.
Preferably the fluoropolymer matrix reinforced with reinforcing substances incorporated in the matrix can be of the type marketed as Chem Coat 1012, or Temp Coat 1008 F, by Impregion Deutschland GmbH. The fluoropolymer matrix provides an antifriction coating with sufficient temperature resistance and the reinforcing substances serve to ensure an especially high wear resistance and thus significantly higher useful lives than with the earlier fluoropolymer coatings. The coating of the invention, simply referred to hereinafter as a reinforced fluoropolymer system, has a friction coefficient against steel of less than 0.1. The coating preferably has a thickness of 15 to 80 xcexcm. This low thickness ensures excellent heat transmission to the sheet steel body and dissipation of the heat generated by the belt upon a crash. In addition, the rerouting device with its reinforced fluoropolymer system emits significantly less noise as the belt is drawn through it than the prior art plastic coated rerouting devices.
The surface provided with the coating can have a nonuniform surface structure so that contact with the belt is limited and this can be obtained by sandblasting and shot-peening of the surface before coating.
The guide surface can be provided with an opening through which a roller extends, the roller journaled between lugs of the usual steel body. The curvature of the frame limits bounding the opening which can run into the curvature of the roller on which the seat belt is guided. The roller limits sliding friction between the fixed surfaces of the rerouting device and the belt to further reduce the frictional heat. The portion of the roller extending through the opening can make up more than 20% and preferably at least 40% of the surface on which the belt is guided.